Peripheral nervous system MCQs

The most sensitive method for detecting carpal tunnel syndrome is: 

A. Needle examination of the abductor pollicis brevis 

B. Needle examination of the first and second lumbricals 

C. Motor amplitude of the median nerve 

D. Motor distal latency of the median nerve 

E. Palmar sensory conduction time of the median nerve

ANSWER Palmar sensory conduction time of the median nerve Eighty-five to 90% of patients with carpal tunnel syndrome manifest abnormalities of the nerve conduction velocities. The palmar sensory conduction time is the most sensitive electrical test for carpal tunnel syndrome. The abductor pollicis brevis (A) and the first and second lumbricals (B) are innervated by the median nerve, but needle examination alone is not as sensitive as sensory conduction time for diagnosis. Decreased motor amplitude (C) is more sensitive and specific for axonal loss. Motor latency (D) of the median nerve is less sensitive than palmar sensory conduction time (E) of the median nerve for the diagnosis of carpal tunnel syndrome.

In the treatment of chronic pain, the undesirable effect(s) that is/are more common in stimulation of the periaqueductal gray than the periventricular gray region is/are: 

I. Diplopia 

II. Oscillopsia 

III. Reduction of upgaze IV. 

Sense of impending doom 

 A. I, II, III 

B. I, III 

C. II, IV 

D. IV 

E. All of the above

ANSWER All of the above Diplopia, oscillopsia, reduction of upgaze, and a sense of impending doom are all more common with stimulation of the periaqueductal gray than with stimulation of the periventricular gray region.

Weakness of the deltoid muscle is caused by injury to the: 

 A. Axillary nerve 

B. Dorsal scapular nerve 

C. Musculocutaneous nerve 

D. Suprascapular nerve 

E. Thoracodorsal nerve

ANSWER Axillary nerve Weakness of the deltoid muscle could be caused by injury to the axillary nerve (A), which innervates the deltoid. The dorsal scapular nerve (B) innervates the rhomboid muscles as well as the levator scapulae. The musculocutaneous nerve (C) innervates the muscles of the anterior compartment of the arm including the biceps brachii and the coracobrachialis muscles. The suprascapular nerve (D) innervates the supraspinatus and infraspinatus muscles. An injury to the thoracodorsal nerve (E) would cause weakness of the latissimus dorsi muscle.

Sudeck’s atrophy, associated with reflex sympathetic dystrophy, refers to atrophic changes occurring in each of the following structures except: 

 A. Bone 

B. Joints 

C. Muscle 

D. Nerve 

E. Skin

ANSWER Nerve The manifestations of Sudeck’s atrophy are late changes of reflex sympathetic dystrophy (CPRS I, RSD). This condition may involve atrophic changes in the bone (A), joints (B), muscle (C), and skin (E), but not the nerve (D). The diagnosis of CRPS I, or re ex sympathetic dystrophy, is made only in the absence of a know n nerve injury (in contrast with CRPS II, or causalgia, which requires a know n nerve injury for diagnosis).

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